A new structure for CuIn1−xGaxSe2 (CIGS) solar cell is investigated. The structure consists of an absorber layer with constant bandgap placed next to the cadmium sulfide (CdS) buffer layer and a graded bandgap absorber layer positioned near the molybdenum (Mo) back contact. This leads to a reduced recombination rate at the back contact and enhances collection of generated carriers by additional induced drift field. The structure provides higher efficiency than previous structures. Optimum value of bandgap, thickness, and doping level of the layers are determined to reach maximum efficiency. Moreover, a trap density model is interpolated and applied in the simulations.

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